In hotel rooms, night train compartments and the like public lodging facilities, a constant concern is burglary. Indeed, the door locks are often of simple construction, for example, with a lock bar pivotally mounted to the interior wall of the door to lockingly releasably engage an aperture in a jamb plate by pivotal action thereof. In its door locking condition, the lock bar usually rests by its own weight against the bottom edge of the jamb plate aperture, normally in a horizontal position; to release same, the room occupant rotates the lock bar counterclockwise (when the lock bar is on the right-hand side of the door) to lift the lock bar away from the jamb plate aperture, in an arc of a circle travel path. Accordingly, the overall vertical length of the door frame jamb plate aperture must be sufficiently greater than the overall width of the lock bar, to provide enough clearance above the lock bar, within the jamb plate aperture, for this upward sweeping motion of the lock bar.
Accordingly, thieves, simply by inserting a credit card or other thin, rigid implement, through the air gap between the closed door outer edge section and the jamb plate, are known to be able to lift the transversely-extending lock bar to pivot same to clear the jamb plate, which is to say, to release the door from the jamb. The door is then unlocked.